Biomonitoring has become a common tool in assessing exposure to a variety of chemicals including persistent organic pollutants (POPs). POPs are typically measured in blood serum, usually requiring a 10 mL whole blood draw or more. Because of the invasiveness of sample collection, infants and children are not typically included in studies evaluating POPs exposure or health effects. Dried blood spots (DBS) are collected from all neonates at birth and are archived by the state health department for a number of years. DBS represent a potential matrix for biomonitoring of POPs. Distinct advantages of using DBS include: (1) they can be easily collected from participant or non-medical personnel; (2) DBS cards are inexpensive compared to blood collection supplies; (3) each state has an archive of DBS from all children born in the state; (4) DBS can be easily mailed from the field to laboratory using standard postal services; and (5) they can be used to collect infant or child blood samples. Despite their advantages, few laboratories have attempted to use them as a matrix for biomonitoring studies. We propose to develop and validate a sensitive, selective and precise method for measuring polybrominated biphenyls, polychlorinated biphenyls and organochlorine pesticides in a single DBS. We will measure these chemicals in 50 neonate DBS samples archived from 1970-1980 in Michigan, a state that experienced a contamination event in the early 1070s which resulted in widespread exposure to certain POPs. These measurements will help us to understand if DBS archived for over 40 years are useful for historic testing purposes and will help us pinpoint the exact year the contamination occurred. In addition, we plan to field test the prospective collection of paired serum and DBS samples shipped to the laboratory on dry ice (overnight) and via USPS, respectively, to determine if they correlate without appreciable bias. This research will not only inform our current cohort study in Michigan but also other studies seeking cost-effective sample collection strategies that can also be used on infants and children.